Such a screw element in the form of a fastening element can be taken as known, for example, from WO 2010/014881 A1. The screw element comprises a shank having a thread. In addition, the screw element comprises a head connected to the shank. The head has a tool engagement portion having six corner domes arranged evenly distributed in the circumferential direction of the head. The corner domes in turn have respective flanks, by which the head can be brought into positive cooperation with a hexagon socket of a tool for tightening of the screw element.
Such a tool is constituted, for example, by a box spanner having a socket which has a tool engagement portion in the form of a hexagon or double hexagon. This hexagon or double hexagon is constituted by a hexagon socket, in which the tool engagement portion or the flanks of the screw elements can be at least partially arranged.
The flanks of the screw element can thus cooperate positively with the hexagon socket of the tool, so that torques, for the screwing down and tightening of the screw element, can be transmitted from the tool to the screw element. By the use of the tool, a person can hence, for example, screw down or tighten the screw element. Between the corner domes in the circumferential direction, respective recesses are arranged. This means that respectively two successive corner domes in the circumferential direction of the head are spaced apart by a recess arranged between these corner domes.